Incest is a somewhat popular topic in English erotic fiction; there are entire collections and websites devoted solely to this genre, with an entire genre of pornographic pulp fiction known as "incest novels". This is probably because, as with many other fetishes, the taboo nature of the act adds to the titillation. With the advent of the Internet, even more of this type of fiction is available.
Besides this, incest is sometimes mentioned or described in mainstream, non-erotic fiction. Connotations can be negative, very rarely positive, or neutral.